First, make a copy of your save games
C:\Users\%USERNAME%\AppData\LocalLow\Tactical Adventures\Solasta\Saves


Then

Open Windows explorer in:

C:\Program Files (x86)\Steam\steamapps\workshop\content

Search for "yendor" with no quotes.

Copy the file
Vel Ode to Yendor.json
to:

C:\Users\%USERNAME%\AppData\LocalLow\Tactical Adventures\Solasta\UserContent\Campaigns

Start Solasta. Go to Dungeon Maker. Select Vel Ode to Yendor without the steam icon. Click Edit.

Increment the version to a higher number e.g. from 1.13 to 1.14

You can either:
1) remove the key items or
2) give yourself the key items

For 1) removing the key items
Select the map Baalzebub's Lair, DL13
Scroll down to the bottom of the maps list and click Edit.
In the southwest corner of the map there are a series of doors. Click each one and hit the Delete key.
Save the map, save the campaign. Load your save game.
It will automatically load the newer version of the campaign.


For 2) give yourself the key
Add a chest near your characters current location
Add the Candelabrum of Invocation as a loot item to the chest


Hope that helps!