Extension is very useful, but for some reason it can`t convert XMR and BNB, although they are on coinbase

not recognize th XMR, BEAM, XHV and maybe other. BTC, ETC, ETH is OK.

Every time I close out and then start Firefox anew, I have to visit this addon's config page and save my preferences again to get it to show up in the context menu.

Additionally, Cryptonator can be limited compared to CoinMarketCap. I'd recommend an option to chose between the two -- the open API of Cryptonator which requires no registration, or CoinMarketCap which would require registration for a free API key.

Been looking for something like this ever since I found it baked into Opera...

You also might want to be a little clearer on how to add additional coin conversions or make it a textbox or list instead.

In settings, just add all the coin abbreviations separated by a space.
Same for fiat