Update No.2, 05.Apr.2020:
X-Axis Clamp added,
V2 is without spacer, V2.1 with Spacer
(naming system is the same: X_V2 = same features linke Y_V2 and so on)
Status: V2 w/o spacer tested successful, V2.1 not tested

Update No.1, 05.Apr.2020:
GT2_Clamp_Ender_5_Y_Carriage_Sling_Beltspacer_v2.1.stl added
(this is teh improved Version 2 but with Belt Spacer, which presses the belt down a bit more into the 2020 Profile, the Spacer is 5mm wide so there should be 0.5mm space left and right in the V-2020 Profile slot)
Status: NOT TESTED

This is my try to design a easy to use fixation, for the belts on the Ender 5.

i designed 3 versions.
One without Sling, (a selflocking design), but i redesigned it, because of the tolerances, while printing, the teeth are not as practical as I hoped.
-GT2_Clamp_Ender_5_Y_Carriage_without-Sling_v2.stl (not recommended)

So i created one, with a kind of sling routing, so the Belt is holding it self.
This Sling Version 1, has also a kind of spacer, wich is 6mm wide, it should push the Belt a bit down, so it runs more straight within the V-Slot.
-GT2_Clamp_Ender_5_Y_Carriage_Sling_v1.stl (not recommended)

But due to sometimes appearing issues with touching the V-Slot, and tolerances at the carriage, and the thing that the Belt has to be shortened, during installation...

I designed a second version of the Sling Clamp. (V2)
There is no spacer anymore, which could produce friction at the 2020 profile and the end for the Sling is open now, so u can leave the Belt as long as u want, (may be for modifications).
...this is:
-GT2_Clamp_Ender_5_Y_Carriage_Sling_v2.stl
-GT2_Clamp_Ender_5_X_Carriage_Sling_V2.stl

and now, there is a Version with a bit smaller spacer, 5mm, to reduce the ability of friction to the 2020 profile.
-GT2_Clamp_Ender_5_Y_Carriage_Sling_Beltspacer_v2.1.stl
-GT2_Clamp_Ender_5_X_Carriage_Sling_BeltSpacer_v2.1.stl

I also attached pictures for installation, and what to loose.
obay lower Belt Routing, its easyer to twist the Belt than i thought.

WARNING: u should disconnect, Y-Stepper, because during adjustment, and Belt installation, u may push the Y-Axis back and forth, and depending of how fast the stepper generates a more or less voltage value, so it is possible, with fast manual moves, to blow ur Board or Stepperdrivers. (again, just pull the Connector at the Y Stepper)

My Sliceer settings for really good results:

Layer: 0.12 (cura Super Quality)
Temp: 195°C
Infill: 50% (cura Triangles)
Support:
for NoSling =Yes
for Sling V1 = Yes
for Sling V2 = No

Wall thickness: 1.2 (3 pcs)
Upper Layers 7
Lower Layers 7
Speed 80
Wallspeed 40
First Layer Speed 20
Support zigzag