How to create my own webapp unity integration?

Solution 1:

Yes you are right. You need to execute that again.

Basically webapps are user scripts which are executed everytime you enter on a determined website (in your case, https://tumblr.com/dashboard), which then provides the integration the website on the Unity desktop.

So if you want to make that "permanent" (execute that code everytime you enter on the website), either you can include that js on the website (if you own it) or use something like GreaseMonkey or TamperMonkey to include that script on websites which you do not control.

Of course, you can also create a package: see the source of unity-webapps-youtube for example.