The Guideline panel Window > Panels > Guideline shows the properties of the currently selected guideline, and allows you to edit these properties:
The set of the properties you see in the panel depends on the type of guideline selected. For example, you can only change the angle for vector guidelines.
You will see the label G-line for a glyph (local) guideline, F-line for a font (global) guideline, and E-line for an element guideline. Element guidelines are created with the Guides tool or Add Power Guides command). You can edit the selected guideline’s name, color, width and type in the panel, as well as lock/unlock it. Remember that a locked guideline can be renamed, but cannot be moved. The position of the horizontal and vertical guidelines, the origin point coordinates, as well as the length and angle of vector guidelines can be changed here. You can also set the guideline tags and see the positions of guideline marks.
Note that guidelines that have a tag assigned to them are only shown in glyphs that share the same tag. Also element guidelines are visible only in the current element.