Keep light equipment from tipping up from cable weight?

I just put a box of ammo on top.  Heavy and dense, they keep everything in it's place.

A chunk of whatever is lying about wrapped in electrical tape. The tape prevents unwanted scuffing of the equipment.

There are a variety of colors of electrical tape available for those with O.C.D.

Blu-Tak is my Blu-Tak is my go-to. Other brands can leave an oily smudge or damage the finish of the component below. Gorilla double-sided tape works well and is much grippier, but also pretty close to permanent. 

Mitch2 #2 is what I use. A similar alternative is moving the component forward on a shelf so the cord is supported by the length of the shelf behind the component.

All of the above. Similar problem with a heavy Transparent PC into my Zenith MK3. I have a Herbie’s Tenderfoot underneath the plug to prevent it’s coming loose (the plug also has a few wraps of plumbers tape). It also prevents the Zenith from tipping due to the weight of the power cord   Between the pc plug and the Tenderfoot is a metal “cradle” like the top unit from a FURITECH NFT support bout cheaply from Alibi which supports the application perfectly.  
 

Unfortunately A’gon doesn’t allow pics so I can’t show you. Email me if you want pics  

i also a Tenderfoot under the back of my Chord DAVE to keep it stable and prevent the front from tipping up.  There are two Tenderfoot sizes depending on how tall your unit is.  They can be combined.  There is also a wooden height extension.