How do I display the same ruler across the Artboard?

[Poto]

I want to display the same ruler line for all three panels so that I can symmetrically align the elements

But I found that the ruler can only be displayed within a Artboard, like the arrow on the left in the picture. But I want the effect of the ruler line pointed by the arrow on the right

in this picture, on the left is the reality, on the right is the effect I want but don't know how to achieve

[walt.farrell]

Guides are specific to each Artboard, and are only displayed on the Artboard that is active for editing.

[thomaso]

As workaround you can draw a line in a separate layer above all Artboards. This will show up on all Artboards and snap, too. In example below: The two bold, dashed lines and their two single "(Curve)" layers.

Disadvantage: once you move such a layer it will automatically get moved by Affinity as child layer of a current Artboard layer. Thus it can unexpectedly disappear and needs to get removed on top of the layer stack.

[Pšenda]

5 hours ago, walt.farrell said:

Guides are specific to each Artboard, and are only displayed on the Artboard that is active for editing.

Yes, that's how Guides work at the moment, but for many situations it would be very useful if they worked globally, that is, for all Artboards. Auxiliary lines, as proposed by thomaso, in turn require that the Artboards must be precisely aligned, which in turn does not allow the use of a global/common guide for the horizontal position (in OP example). An alternative would be to use the Symbol (name Guides), which would be copied to all Artboards. Any adjustments to it, both vertical and horizontal, would then be transferred to all Artboards. Symbol would have to turn off before exporting, which would probably be the only case where wrong and years of uncorrected implementation of shutting down all instances of the symbol will be welcome.