I need to add at least two links in the footer under both - osticket and osawesome - logos.
Any idea how to do that with the custom css instead of changing any standard file?
Thanks and best regards
Nope, that is outside of what CSS is designed to do. CSS is primarily for styling HTML elements.
The only way I can think of to insert links without touching the source code would be to use Javascript or jQuery. But that would require a fairly sophisticated programing solution and isn't worth the trouble.
But if you did want to edit the source code, it isn't really a big deal. The only caveat is that you'll want to back up the edited file(s) when upgrading and apply your edits to the new installation. Super easy!
The file(s) you'll edit are:
osta/inc/client-foot.html
osta/inc/staff-foot.html