toolbar across top too small for me to clearly read
It seems you may be referring to the menu bar. In Linux Mint, I can adjust the system default font. This of course will affect more than just the menu as well as other applications.
I am referring to the LibreOffice toolbar - I do not know Linux Mint - or even what that is. I have found several sets of instructions for enlarging the toolbar font - they work in Libreoffice 5.2 but Do Not work in Libreoffice 6.2. I have 6.2 and so does my husband who is having great difficulty reading the toolbar at all.
Linux Mint is an operating system like Windows or Mac OSX. The change I mentioned does also change most of the font in toolbars. The exception here is when using the Tabbed ‘ribbon’ toolbar not all text conforms to the change.
There are numerous duplicate questions on this site.