After adjusting the line-guides in CorelDRAW you can lock them to avoid accidental displacement.
Select one or more guidelines (or all), that you wish to lock and go to: Arrange > Lock object [Fig. 1]. To unlock Guideline(s) do the reverse action: click on Arrange > Unlock object [Figure 2].
Tip provided by Silvio Gomes, CorelDRAW Master, Artist and Graphic Designer.