Using the /execute store command to store values in an item doesn't work. I don't know what the problem is, but as far i tested, it only applies when trying to store values in items in 1.15.

This command should set the Damage value for my selected item to my "Test" score, but nothing happens to the item when i execute it.
/execute store success entity @s SelectedItem.tag.Damage double 1 run scoreboard players get @s Test

For some reason, /execute store does work when i try to store values in entities, like with the command below.
/execute store result entity @e[type=iron_golem,limit=1,sort=nearest] Health double 1 run scoreboard players get @s Test

By the way, my "Test" score is set to 10.

I've been testing the most recent snapshot(s) to see if this got fixed for a while now, and seeing how it hasn't been yet, i decided to report it.

I'm sorry if the report isn't decipherable, first bug report, and English isn't my first language.