If your screen is small and the Windows "Display scaling factor" is relatively high then you may be below the minimum 1440 x 900 dpi effective resolution required for correct display of all SnapGene windows. See What are the System and Hardware Requirements for SnapGene?
For older versions of SnapGene (5.0 or earlier) see Windows:Screen Resolution/Scaling Issues (SnapGene version 5.0 or earlier).
SnapGene requires a minimum effective resolution of 1440 x 900 dpi. On some Windows computers with smaller screens and high scaling settings, SnapGene windows may be cropped and buttons or menus may be "offscreen" and inaccessible. To resolve this issue try the following options:
Option 1: Set the Preference to "Prefer Smaller UI"
Start SnapGene, then click menu Edit → Preferences and select General from the side bar.
Check the Option "Prefer Smaller UI".
Click OK to acknowledge that you need to restart SnapGene for changes to take effect.
Click the Close button in the top right corner of the Preferences window to close the preferences. If you can't see the close button, then type CTRL – w to close the window.
Exit SnapGene.
Start SnapGene, if your screen resolution is sufficient then SnapGene should now display correctly.
If the SnapGene still does not display correctly then try changing the Windows Settings → System → Display "Scale" setting to a lower value. Otherwise try Option 2 below.
Option 2: Set a custom QT_SCALE_FACTOR Environment Variable
Click in the "Search" box in the Taskbar at the bottom of the screen.
Type to search for "env", then click "Edit the system environment variables".
Click on Environment variables to open the "System Properties" Control panel.
Click Environment Variables....
Under section "User variables" Click New....
Set the "Variable name" to QT_SCALE_FACTOR and the "Variable value" to 1.01 then click OK to close the dialog.
Click OK to close the Environment Variables window.
Click OK to close the "System Properties" window.
If SnapGene is running then go File → Exit (CTRL-q).
Restart SnapGene to use the new settings.
If the resulting scaling within SnapGene is to large or to small then repeat the above procedure and set the value to whatever looks best such as 1.1, 0.9, or 0.75, 0.5 etc.
Ensure you exit and restart SnapGene each time you change the QT_SCALE_FACTOR value to ensure the change takes effect.