Looks ok for me.
screenshot ?

underground Lines buggy with white Placeholders ?

1.5 update (was still working)
Dropped support for PowerSwitch mod - they dropped support their invincible power lines, they are now vanilla so this mod use vanilla defs.
Possibly will drop Underground Power Conduits in future.

at some stage but unlikely to be done in next 2 months

Are there any plans to update this for RimWorld 1.4?

All three mods have been updated to 1.4 now: "Parallel Power Grid (Parallel Conduits)", "PowerSwitch" and "Underground Power Conduits".

Fixed. tested both mod variants. Since PPG and UPC have its own groupings there are two power conduit groups.
PS did not have any grouping, so I did one similar to UPC one.

LMK if you want me to merge them into single one so all conduits (underground, waterproof, parallel, will be under one button)

Right - PPG have it's own grouping done and link tags changed.

continued..

Verse.Root/<>c:<Start>b__6_1 ()
Verse.LongEventHandler:RunEventFromAnotherThread (System.Action)
Verse.LongEventHandler/<>c:<UpdateCurrentAsynchronousEvent>b__27_0 ()
System.Threading.ThreadHelper:ThreadStart_Context (object)
System.Threading.ExecutionContext:RunInternal (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool)
System.Threading.ExecutionContext:Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object,bool)
System.Threading.ExecutionContext:Run (System.Threading.ExecutionContext,System.Threading.ContextCallback,object)
System.Threading.ThreadHelper:ThreadStart ()

[Parallel Power Grid (Parallel Conduits) Addons] Patch operation Verse.PatchOperationAdd(/Defs/ThingDef[@Name="ParaCond"][not(designatorDropdown)]) failed
file: C:\Program Files (x86)\Steam\steamapps\workshop\content\294100\2059429490\Patches\HideClutter.xml
UnityEngine.StackTraceUtility:ExtractStackTrace ()
Verse.Log:Error (string)
Verse.PatchOperation:Complete (string)
Verse.LoadedModManager:ClearCachedPatches ()
Verse.LoadedModManager:LoadAllActiveMods ()
Verse.PlayDataLoader:DoPlayLoad ()
Verse.PlayDataLoader:LoadAllPlayData (bool)
Verse.Root/<>c:<Start>b__6_1 ()

Getting an error message, and I'm not seeing underground parallel conduits. I tried uninstalling "Underground Power Conduits" and the underground parallel conduits appeared, but they wouldn't connect to the sockets. Any idea? Thank you!!

should be fine - fixing different mods now. It's on my list.

1.3 anyone?

Added groups for battery/socket/etc to remove clutter.

Corrected graphics.

OK, "Underground Power Conduits" had issues.
Visuals is same as "Power Switch".
Fixed beauty and placement of colored and non-colored one - parent class was wrong so it actually place underground colored and normal (overground) cable. Fixed some typos also.

So yes
Power switch underground cable is actually transparent texture rendered on floor - this is why it's not shown. AFAIK Rimworld does not have layer definition to hide (visually) under floor.
Only option to not show tem (as much) will be to use different texture (with alpha channel set differently) so they will look almost transparent, or much thinner - can't promise this as whole mod i hacked in 30 mins and my graphics skills are very limited.
Also, color underground and normal underground can be placed on same tile - gonna check now how "Underground Power Conduits" behave.

Beauty is same as underground (0-value)
Texture hide might not work, as for normal underground is transparent png, color ones use PPG mod textures.
Building them in one grid should work, but will try.

Correction: I cannot built a underground color conduit over another wunderground noncolor conduit

I have underground power conduits. Although beautiness is not affected by an underground color conduit, it is not hidden by soil, or even floors, it's visible. Furthermore, I cannot built one on the same tile as walls or anything else.

They are not dependencies actually - not having them will not add their functionality, but I'll add links in description.

It might help to have links to the supported mods in the description. That way if someone likes your mod they can find the dependencies more easily.

RTSwitch - moved parallel conduits to group and they are accessible from underground button (less clutter)
Added support for "Underground Power Conduits" (not really tested)