Manual dimension values?

I have drawn a part which is quite long, but only the ends need detailing, so I draw the length "not to scale" and indicating this by drawing double slashes through the part.
Adding the dimension then obviously shows a wrong value. In AutoCAD I could call up the properties and change this - either to a number or a letter - in LibreCad the only way I found is to explode the dimension, delete the number and put a text in. That, however, loses the connection of the dimensioning to the reference points.
Is there a way to keep the reference, but input a "manual" value?

You can override the dimension text via "Properties".

Question that I also have had but very new to LibreCAD and would appreciate some more hand holding to help me find "Properties."  
Ed

Tools - Modify - Properties. Then select the dimension and you get a box where you can put in new dimension label.

You can also select the dimension, enter "mp" in the command line (modify property) and type your text on the right side of the opened window.

Got it.... Many thanks.  Often sketch a woodshop project and then change my mind on a dimension, or modify on the fly, then want to document.  This is a simple fix where an accurate to scale drawing is not required.