If you find the āmanualā save mechanism that Mark mentions inconvenient then you might like to take a look at TiddlyDesktop which gives a more convenient save mechanism together with an autosave backup feature - a similar feature for your mobile device is Tiddloid, I run them both - TiddlyDesktop on my Linux laptop and Tiddloid on my android phone - although they are different apps I find the experience of using them alternately seamless, the only manual operation being exporting the odd updated tiddler from my mobile devices to my laptop master - I just finished updating my master after being on vacation where I only had my phone with me.
Donāt think badly of Tiddlywiki for the awkward manual save mechanism - it is a consequence of the fact that TiddlyWiki is designed to run as a single, standalone HTML file which is what makes it so portable - your browser is designed to protect you and that is why the save mechanism ends up being a regular browser download file with your consent being necessary - Tiddlywiki is in effect just another webpage and no-one wants general webpages downloading files to their machine adhoc.