How about add custom option for synchronisation interval (you can choose number and min/hours/day) or add maybe shorter time maybe 1/2 min?
Hello, and welcome!
Why would you want that?
For example: I open Joplin on PC, create a new note and close in less than 5 minutes, the note won’t be available one other device. I have to click it synchronise button.
And it’s nice to have option to synchronise when you close/open Joplin
I see. I may be wrong, but IIRC Joplin originally synced much more often, but then the interval was prolonged so it wouldn't sync constantly.
Maybe you could use manual syncing as a workaround? Don't forget you can trigger a sync by hitting ctrl + s, and if you've only edited a note or two, the sync will finish in a second, so you can close the app again.
(I like to keep Joplin running. But that's just me. 
)