Your bike is no longer roadworthy? Your running shoes already have a hole in the sole?
Time to retire them!

How to sort out old equipment such as shoes or bicycles

Specify an end date in the usage period for the equipment item.

Click with the mouse on the edit icon on the far right of the equipment item row.
You may have to move the table to the right.
Also, make sure that you have selected the usage period column for display.

After saving, the item appears grayed out at the bottom of the table.