Delete everything following line 100

[DigitalVolcano]

You can blank the lines after 100 the following way:

Click on the 'Limit to lines' tab and set 'From line' to 101. Uncheck the 'To' option.

Then, Click on the Regular Expression tab and set:

Regex:
.*
Replace:
(leave this blank)

The only issue with this is that it leaves blank lines after 100 rather than removing the lines. You'll then need to remove them in another pass using a regular expression:

Change back to 'Read entire file' (not limit to lines)

RegEx:
\s*$
Replace
(leave this blank)

Make sure the 'dot matches newline' and 'multi line anchors' options are not checkmarked.