Export pane in LRC 12.0.1 on my PC not showing enough space for dropdown menus to select preferences

"Sorry so blurry. How can I fix it?"  Presume you mean the photo of screen.

Use a screen-clip app in Windows instead of a camera photograph of the screen.

"I cannot access the contents in the dropdown menus like watermarks,"

You need to place a check mark in the watermark option box before you have access to a drop-down menu.

But, yes, I do see that your panels are truncated so as to 'hide' a top portion of each panel.

Try resetting the LrC preferences. PREFERENCES RESET 

Moved to the Lightroom Classic forum from Using the Community