Using Windows 11
I'm sorry I didn't get back to you sooner. To use developer mode, I did copied the command from the help menu. Then closed Joplin and ran the command. I was afraid to have 2 versions open. My Joplin is precious. Each database is in a separate folder.
I'm updated to v0.1.0
I copied a 7 or so page essay I wrote quickly to a new note, so it'll have a lot of stuff. I had lots of wrong red lines because I was defining Sanskrit words. However, it was impossible to use the system. All the red seemed to be spelling. There were lots of yellow marks. I could not figure out how to make them work. I tried one click, two clicks right clicks and left clicks. Nothing would happen for perhaps 20 or 30 seconds. I could go looking somewhere else and something would pop up. Sometimes it would go away, sometimes it would offer a suggestion, so then it was LanguageTool. But, sadly, it seemed to appear only on about 10% of the attempts and after so long, I wasn't there anymore.
Since it isn't working right, I need to know exactly how to work it. For example I left out the comma after example in this sentence. I got an orange underline. When I left-clicked the word and this appeared. This is what Firefox does.

Nothing I did created a response in less than 15 seconds, and then only about 10% of the time.
My computer is pretty good. Within Firefox it works immediately, so something is wrong.