Hello and welcome @Bart 
You could create an url to open the composer for a PM to a specific user or group if thatâs any use?
Eg. âSend a PM to community moderatorsâ
You can find more info here - Create a link to start a new personal message with pre-filled information
(You may also need to set âwho can message this groupâ to âeveryoneâ from the group settings)