The Total Packs provide a user-friendly interface for tweaking and playing custom levels.
Their official forum thread can be found here.
Below is an overview of all the Total Packs (PoP1, PoP2, C64).

PoP1 Total Pack

Download for Windows: PoP1_Total_Pack_v3.5.zip (15MB)
Version 3.5 was released by starwindz on 9 April 2017.

Important: to fix the "Invalid Enum Value" error, edit ini\mirror_sites.ini and change 3x popot.org's http to https.

Some old versions:
- v3.01 (3 March 2017): PoP1_Total_Pack_v3.01.zip (14MB)
- v3.0 (23 September 2013): PoP1_Total_Pack_v3.0.zip (14MB)
- v3.0b1 (13 September 2013): PoP1_Total_Pack_v3.0b1.zip (12MB)
- v2.06 (19 January 2008): pop1tp_v206_full.exe (20MB)

PoP2 Total Pack

Download for Windows: pop2tp_v011.exe (9.1MB)
Version 0.11 was released by starwindz on 3 August 2007.

C64 Total Pack

Download for Windows: poptp_c64_v1.0.zip (2.8MB)
Version 1.0 was released by starwindz on 29 December 2011.