Probably silly question from noob mapper

I’ve just started mapping, added a few local paths & POI, only using Potlatch, and I could not find a suitable tag for a public open-air tennis court. Having marked the relevant area (or simply POI) I thought I would find a sport=tennis tag but it’s not there in Potlatch. Table tennis is there! but not tennis !
Do I have to use JOSM to get a wider choice of tags?
I used sport=raquet as temporary measure but not really comfortable with that…

No, you don’t have to use JOSM. You can add any tag you like in Potlatch by using the ‘+’ button.

If it is not in the presets of %OSMEDITOR% it doesn’t mean it doesn’t exists: and search for “tennis”

I use;

Same for basketball/volleyball courts.

Can’t find anything else under *leisure *which would be more appropriate.