As I have shamelessly abandoned my mod, here are the links to the alternatives. The first two are updated versions of this, while the third one is a new mod by one of the devs with a slightly different approach:

https://mods.factorio.com/mod/BlueprintLab_Bud17
https://mods.factorio.com/mod/BlueprintLab_Bud18
https://mods.factorio.com/mod/Edit-Blueprints

PS: This is my first mod. Any comments and criticism is welcome. Thanks a lot to all mod authors and tutorial writers, from whose work I could learn to work with Factorio, this wonderful game.

Forum Thread: Click!

Enter your lab to design your blueprints.

When you go into your lab, you will leave your character behind. You cannot bring anything into the lab from the outside world and vice versa, except blueprints. While in the lab, cheat mode will be activated and you will find an infinity chest and an electric interface. Use these to design your blueprints.

Current Features:

• The lab is a 512 by 512 featureless space for designing blueprints. You can go to the lab via the lab button in the top left or via the lab hotkey (default: Shift + B).
• When you go to the lab, you leave your character and inventory behind. But if you do so while holding a blueprint or a blueprint book, you will bring a copy of it to the lab.
• In the lab, cheat mode is enabled. Also, an electric interface and an infinity chest are provided.
• In the lab, ghosts are instantly revived and items marked by the deconstruction planner are immediately destroyed.
• You can return from the lab by clicking the lab button or activating the lab hotkey again.
• You cannot bring back items from the lab. But if you return while holding a blueprint or a blueprint book you will bring it back to the world.
• When you return from the lab any non-empty blueprints or blueprint books in your inventory are dropped to the ground. All other items in your inventory are destroyed.
• The lab is persistent and in multiplayer each force has its own separate lab.

Planned Features and Known Issues:

• Bring the player back to the world if their character takes damage.
• Improve the GUI: Use a smaller and more interesting button with a stripe.
• Currently the lab has a fixed size, I would like it to have an unlimited size. But it seems difficult to fight with the world generator. The current model mimics code from Factorissimo2.
• An optional (and single player only) ability to pause the game (the rest of the world, the other surfaces) while in the lab. I am not sure if this is possible.

Version History:

0.2.4 - Underground belts, splitters, and loaders are also properly cleared.
0.2.3 - Labs placed in the lab are now inactive, i.e. no research exploit.
0.2.2 - Blueprint transfers added. Russian locale (thanks to ZwerOxotnik) added. Bots and belts are now properly cleared.
0.1.2 - Fixed a bug due to needlessly recreating the interface. Added a proper migration script for 0.0.1.
0.1.1 - Fixed a nil reference bug that occurred when loading a save game from 0.0.1.
0.1.0 - Implemented lab hotkey, clear button, instant ghost revival, revival and deconstruction events, localization and tooltips.
0.0.1 - fixed setup when adding the mod to an existing game.
0.0.0 - initial release.