How to Shrink Archive List in WordPress

First, you need to install and activate the Compact Archives plugin.

After activating, go to Appearance >> Widgets page and drag-drop the 'Compact Archives' widget to your sidebar. Then select the style for your archive.

The Compact Archives plugin comes in three styles. You can choose from block, initials, or numeric.

After making the settings click on the Save button. Now you can go to your WordPress website.