If your goal is to replace them use the replace function under menu tools:
replace them with nothing or do specifice replacements:
Thanks to Pim, who gave me a clue I was able to find all the buttons and was able to do what i wanted to do, which ended up in a mendix shortcoming/bug: "Changed objects without changes"(even in Mx 7.8.0):
-I changed the clyphicon to a image which is not used within the application:
Now I was able to see all changed pages(marked with the yellow circles) which contained the previously Glyphicon and I'm able to find the usages of the image: Great!
I was able to change the microflow behavior behind some of those buttons.
- I want to change back the Image to the previously glyphicon which on which I would expect that those yellow circles would disappear on untouched pages (same as when you change some text and change it back to its original text).
As shown above: There are no changes on the page, but the page is marked as changed!
To clean up my commit I had to revert all those pages
Anyway thanks again Pim for the clue who helped me to do what i wanted to do.