Of course, the @alan-kilborn solution works nice ! But, as you said :

You could then use Find and Replace to change the size of the label for many hundreds of placemarks.

I’m thinking about an second solution !

For example, from this INPUT text, part of your KLM file :

...
...
<LabelStyle>
<scale>0.9</scale>
</LabelStyle>
...
...
...
    <LabelStyle>
        <scale>37</scale>
</LabelStyle>
...
...
  <LabelStyle>
  <scale>100</scale>
  </LabelStyle>
...
...

Using the regex S/R :

• SEARCH ^(\h*<LabelStyle>\R\h*<scale>)\d+(?:\.\d+)?(</scale>\R\h*</LabelStyle>\R)

• REPLACE ${1}3.7${2}

It would change the size of any label to the 3.7 value and you’ll get the OUTPUT text, below :

...
...
<LabelStyle>
<scale>3.7</scale>
</LabelStyle>
...
...
...
    <LabelStyle>
        <scale>3.7</scale>
</LabelStyle>
...
...
  <LabelStyle>
  <scale>3.7</scale>
  </LabelStyle>
...
...

Thus, although I miss something obvious, no need to get each block of 3 lines in a single line !

In addition, like the @alan-kilborn’s regex, it does not mind about the kind of EOL, which can be, either a Windows, Unix or Mac line-break !

Just place, in the replacement part, your desired number between the two values ${1} and ${2}. For instance :

• ${1}100${2}

• ${1}0.05${2}

• ${1}0${2}

• ${1}12.3456{2}

Best Regards,

guy038

Alan you are a genius

Well. Ahem. Credit for the base formula goes to its author; see the link I provided.

Unbelievable … I’m sitting here at my desk and shaking my head … I still can’t believe it … Alan you are a genius !!! … the formula looks soooo complicated … but … it worked exactly as I wanted it to

Alan thanks a lot !!!
This is something I will never forget
Thank you !!!

or even like this ?

<LabelStyle><scale>0.9</scale></LabelStyle>

Try:

Find: (?-si:<LabelStyle>|(?!\A)\G)(?s-i:(?!</LabelStyle>).)*?\K(?-si:\R)
Replace: make sure this box is empty
Search mode: Regular expression

It’s an application of a technique discussed HERE. It’s a bit of an advanced thing for your problem, but it works.

However, I’m concerned that you may not have stated your problem correctly–we shall see…