As @corradoventu says, what you’re running can matter.
I’m using Ubuntu resolute and logged into a Lubuntu/LXQt session currently, and I can use Ctrl>+ to increase the size of the text on this firefox window… If I was using a terminal I’d use the same key, in fact it worked with both open qterminal and xfce4-terminal terminals I have open, plus my featherpad text editor… To reduce size I’ll just use Ctrl>-
That will not work with a time on the panel, as configurations for panel are set via Configure Panel, and as I don’t have a release, the link I’ll provide matches my own resolute, ie. https://manual.lubuntu.me/master/5/5.1/lxqt-panel.html (adjust URL to match your unstated release; ie. replace MASTER [in url] with STABLE if using 25.10, or LTS if using the older 24.04 to see the appropriate manual for your unstated release)
I skipped that sorry, but in this EDIT post window (REPLY or CREATE TOPIC is identical) there is a picture icon which is what is used to UPLOAD or use a picture
FYI: I actually stole that [example] image from Getting the Most Out of Our Discourse Part 3: The Importance of Topic Lifecycles where @rubi1200 has written a number of posts recently about getting the most of Ubuntu Discourse - they’re well worth a look !