And you’ll be doing this using the Registry Editor.
Step 1 : Go to Start and open > Run (OR) Press Windows + R and then type the command regedit which opens up the Registry Editor.
Step 2 : Now go to HKEY_CURRENT_USER > Software > Microsoft > Windows > CurrentVersion > Explorer > Taskband !
Step 3 : On the right side column of the editor just right-click on an empty space and create a New DWORD (32-bit) Value and then name it as MinThumbSizePx.
Step 4 : Now again right click on this DWORD and choose Modify.
Step 5: Select the Decimal in Base section and set a value of your wish. Put it around 300-400 it’ll be Good.
Now you can vary the size value and adjust it according to your need. And get a Bigger Taskbar Thumbnail 🙂
And if you want to get back your default settings you can just simply delete the new DWORD that you have created.