I've been having some issues where if I leave a world to copy the string into the mod settings (since it falls under startup settings and can't be modified in-game) then all of my tweaks are erased. If I try to make a tweak but something goes wrong that needs troubleshooting (impossible recipes, invalid recipes that don't load, etc.) then I have to manually duplicate the tweaks and re-enter them which can be really tedious for large or involved recipes. For example, I've added some of Bob's mods as standalone mods to a post-game world and those mods don't add the recipes retroactively for existing researched techs causing recipe softlocks and required multiple edits to the tweaks to get to work but trying to troubleshoot it was super tedious cuz I had no way to edit a copy of the tweaks I'd already set. So like for example say I changed science to require wood but then wanted to craft wood with a different item after the first tweak was applied, I'd have to go back into the recipe tweaker and set the wood science recipes on top of the crafted wood edit as the wood science tweak would be deleted in the tweak editing interface. If there were a way to import a string into the gui you could just copy the string you pasted into the settings to pull up the tweaks you were already working on instead of losing them.

Recipe Tweaker is supposed to keep track of what recipes you've made changes to and have them show up in the gui automatically, that way you can add to the changes over the course of multiple relaunches. This removes the need to import changes into the gui completely, but from what it sounds like it's not happening for you.
I have no idea why it wouldn't, but I do know that there's a command for reloading technology effects, like recipe unlocks:
/c game.player.force.reset_technology_effects()
I've never heard of anyone having that issue before, and I haven't been able to replicate it so I don't even know how to start trying to fix it, the code for that part is quite simple and I don't see how it could go wrong. Sorry you're having a problem with it! Are you doing anything besides making a tweak, copying the string, pasting in startup settings, pressing confirm and waiting for reload, then going in game? Those should be the only things you have to do.