Hi, Cornel.
I did a quick test and, yes, but it’s clumsy. You can enter Unicode or copy from the Windows Character Map app. For example, to enter an degree symbol, hold down ALT while typing the decimal unicode value “0176” and release ALT.
I tried copying from LibreOffice Writer in hopes that it would paste in Unicode. That didn’t work. So, if you have significant amount of text that needs to be formatted, you’re probably better off printing the schematic to PDF or SVG and editing in Inkscape. See Printing Schematic To SVG -- Solved?. Also: Insert ASCII or Unicode Latin-based symbols and characters - Microsoft Support.
Maybe someone else has found a better solution…
–robert