We have the same issue but for Sophos, I've followed their configuration guide but I'm unable to pre-approve the "filter network content" pop-up...
You need to create a content filter with the identifier & network filter bundle (you might need the socket filter set too), and it need to be deployed on the machine before the software is installed. Like jonlju, i use one for sophos, in my case it doesnt prompt in my case, but it also does not seem to work correctly either. Other filters work fine.
Thanks @SCCM, I never realized and I've now added that to our configuration profile as well.
To @dan_ashley, maybe it would help reaching out to Fortinet to see if they have a guide for setting up the content filter configuration profile? I tried googling myself but can only find iOS guides.
Thanks @jonlju for the suggestions... Googling for over a week didn't really help & Fortinet support was pretty useless when reached out to them. But through persistence combined with trial and error I have now found that implementing the following settings as part of a configuration profile does the trick for macOS:
OPTIONS > CONTENT FILTER
FILTER NAME = com.fortinet.forticlient.macos.webfilter
IDENTIFIER = com.fortinet.forticlient.macos
SOCKET FILTER BUNDLE IDENTIFIER = com.fortinet.forticlient.macos
SOCKET FILTER DESIGNATED REQUIREMENT = identifier "com.fortinet.forticlient.macos" and anchor apple generic and certificate 1[field.1.2.840.113635.100.6.2.6] /* exists */ and certificate leaf[field.1.2.840.113635.100.6.1.13] /* exists */ and certificate leaf[subject.OU] = AH4XFXJ7DK
NETWORK FILTER BUNDLE IDENTIFIER = com.fortinet.forticlient.macos
NETWORK FILTER DESIGNATED REQUIREMENT = identifier "com.fortinet.forticlient.macos" and anchor apple generic and certificate 1[field.1.2.840.113635.100.6.2.6] /* exists */ and certificate leaf[field.1.2.840.113635.100.6.1.13] /* exists */ and certificate leaf[subject.OU] = AH4XFXJ7DK

Thanks for the suggestions. I had been Googling for over a week with no success and found Fortinet support to be useless when reached out to them. But through continued persistence combined with trail and error I've eventually manage to put together a solution that works. Implementing a configuration profile as follows has done the trick:
OPTIONS > CONTENT FILTER
FILTER NAME = com.fortinet.forticlient.macos.webfilter
IDENTIFIER = com.fortinet.forticlient.macos
SOCKET FILTER BUNDLE IDENTIFIER = com.fortinet.forticlient.macos
SOCKET FILTER DESIGNATED REQUIREMENT = identifier "com.fortinet.forticlient.macos" and anchor apple generic and certificate 1[field.1.2.840.113635.100.6.2.6] /* exists */ and certificate leaf[field.1.2.840.113635.100.6.1.13] /* exists */ and certificate leaf[subject.OU] = AH4XFXJ7DK
NETWORK FILTER BUNDLE IDENTIFIER = com.fortinet.forticlient.macos
NETWORK FILTER DESIGNATED REQUIREMENT = identifier "com.fortinet.forticlient.macos" and anchor apple generic and certificate 1[field.1.2.840.113635.100.6.2.6] /* exists */ and certificate leaf[field.1.2.840.113635.100.6.1.13] /* exists */ and certificate leaf[subject.OU] = AH4XFXJ7DK

Thanks for the suggestions. I had been Googling for over a week with no success and found Fortinet support to be useless when reached out to them. But through continued persistence combined with trail and error I've eventually manage to put together a solution that works. Implementing a configuration profile as follows has done the trick:

Thanks for the suggestions. I had been Googling for over a week with no success and found Fortinet support to be useless when reached out to them. But through continued persistence combined with trail and error I've eventually manage to put together a solution that works. Implementing a configuration profile as follows has done the trick:

How did you find the correct Filter Designation Requirements? I'm facing similar issues with a different application.
How did you find the correct Filter Designation Requirements? I'm facing similar issues with a different application.
I used the PPPC Utility to get the info for the FortiClient app to give me the Filter Designation Requirements, then swapped the identifier to that which was being presented in the popup macOS was presenting.

I used the PPPC Utility to get the info for the FortiClient app to give me the Filter Designation Requirements, then swapped the identifier to that which was being presented in the popup macOS was presenting.

Perfect, this will help me a lot, thank you!
Does anyone know if this changed in FortiClient 7.0.1?
Thanks @jonlju for the suggestions... Googling for over a week didn't really help & Fortinet support was pretty useless when reached out to them. But through persistence combined with trial and error I have now found that implementing the following settings as part of a configuration profile does the trick for macOS:
OPTIONS > CONTENT FILTER
FILTER NAME = com.fortinet.forticlient.macos.webfilter
IDENTIFIER = com.fortinet.forticlient.macos
SOCKET FILTER BUNDLE IDENTIFIER = com.fortinet.forticlient.macos
SOCKET FILTER DESIGNATED REQUIREMENT = identifier "com.fortinet.forticlient.macos" and anchor apple generic and certificate 1[field.1.2.840.113635.100.6.2.6] /* exists */ and certificate leaf[field.1.2.840.113635.100.6.1.13] /* exists */ and certificate leaf[subject.OU] = AH4XFXJ7DK
NETWORK FILTER BUNDLE IDENTIFIER = com.fortinet.forticlient.macos
NETWORK FILTER DESIGNATED REQUIREMENT = identifier "com.fortinet.forticlient.macos" and anchor apple generic and certificate 1[field.1.2.840.113635.100.6.2.6] /* exists */ and certificate leaf[field.1.2.840.113635.100.6.1.13] /* exists */ and certificate leaf[subject.OU] = AH4XFXJ7DK

Hi @dan_ashley
I have a similar requirement for one of the application. I am not able understand the "Filter Name" part. Is it somewhere which we can find out, or is it just a value we give for our reference ? If we can find it out , how do we do it ?
Anyone else having issues with this when upgrading from a previous version of Forti (in my case 6.4.3) to 6.4.6? It doesn't seem to use the network filter after upgrading.