1. Make the Enter key work in the Search box in the User manager, Now you have to click on the search Icon to start searching.

It already works with enter. In the input that says "Search Users..." type "test" then press enter and it'll submit fine.

2. Possibility to hide the Tools 'Load Sample Data' and 'Load Canvas Layout' via the configuration. Aren´t these run-once commands and unnecessary once they are used?

That depends on your situation. If you change the layout and want to reset back you can. If you delete the sample data fields, but decide you want them back you can.

Having done a Little more checks I find it works fine on FF but not on IE 11. Tested on two PCs.

Works fine on Edge so seams to be browser issue that they've already addressed or possible a setting in the browser.

Agree. I am refering to K2, that has a similar function for importing Joomla articles. You can toggle the Import button on/off in the K2 config. I personally find that option useful to avoid unintentional clicking.

I think we just need to ensure all the tools have confirmation dialogs. Then each would be a 2 click usage to avoid any accidents. Would that work for you? We really don't want to add parameters like this as it just contributes to parameter bloat.

Great, have added a feature ticket for this.

forge.joomlapolis.com/issues/5581