Please follow these steps to bookmark (star) a playable version:
Navigate to the playable in Playground
Find the version you wish to bookmark and click the star icon to the left of its name
You can also add tags in the Edit page, to do this please follow these steps:
Navigate to the playable version in Playground and open it
In the bottom right of the page click into the text box under "Playable tags"
Enter a tags one by one, seperate them by hitting enter.
Be sure to then click Save at the top right of the page
These tags will then appear under the tags drop down menu when viewing the different versions of your playable, selecting tags from this drop down menu will filter your versions down to those containing them.
You can read more about this here.