Okay, folks, I actually did it. I had Claude.ai write me a script to convert my DavidRM "The Journal" to the Daylio CSV format, and successfully imported them into Diarium. It wasn't super easy. It took many revisions of the script to finally get something that worked, but now I finally have all my old journal entries in Diarium.
After wanting to do this for months and finally getting it done, however, I'm disappointed to report that I'm not loving Diarium after all. The thing I really don't think I can live with is the "search" function. I NEED what The Journal does (and what Google does, and any reasonable search engine), where when you search it shows you the actual text where it found the search term. Diarium just shows the entry header and first few lines, not necessarily where the text was found. And even when you open the entry, the search terms and not highlighted or anything. Ridiculous! I would have to wade through every entry to find what I was looking for.
So, I don't think I'll be using Diarium until/unless that is addressed.
I also found, in my brief trial of using Diarium, that I really missed the "tree" style navigation that The Journal has on the left side. I keep it all collapsed but I can quickly jump to a year, then month, then day in that tree when I want to browse around.
So, those are some things that ex-The Journal users might find hard to adjust to!
I thought I would share my conversion script in case it can help anyone else. Apparently I'm not allowed to upload it here, though, and it seem there's no way to send a private message here. So, I guess, if somebody really wants to try it, they can post here their email address? I'd say not to post it right out or you'll get a ton of spam but write it out in words like "someone at gmail dot com". If anyone does this I will send them the script.
Just as a caveat, if anybody is going to try this, I should warn you that I designed it specifically to work with the way I use The Journal. I ONLY use the "Daily Journal" category and not any of the other functionality, so I didn't bother with those. The export does "text only" so you lose any pictures you may have attached. I use the first line of the entry as the title, so my conversion script puts that in the Daylio "title" column. There are problem a ton of ways various people use The Journal that will break this script, and I don't have the bandwidth to help troubleshoot. But just on the off chance somebody wants a simple text only conversion, this might work for them.
JP