Themes

QueenNini - The theme will stay your theme as long as you want. No different than using it on Chromium or Chrome. But if you want to default back to the non-theme (system or light) you have to follow the instructions on the website on how to delete out the theme from your browswer. It's actually very easy, I did a few times already and it takes no more than a minute. MS hasn't added a "reset to default" option yet  to their appearance settings. Edge is able to run those themes from Chrome store because technically Edge is using the Chromium browser engine. Google however seems to block the actual use of their Chrome themes on Edge which I wasn't sure if that was in case into I confirmed through research and experimenting a few days back. In other words Edge can use it because they share the same source engine with Chrome (which is Chromium) but it seems Google is not letting them use their Chrome themes on Edge even though per source engine it's compatible (i.e. you can't play with my toys even though we share the same parents). So we have to backdoor it. Maybe eventually Edge will add a reset to default for appearance switch or Chrome Store will allow without blocking the use of Chrome themes on Edge.