Stacking booster or overdrives pedals is pretty common.
But it can also be worth it to stack delay pedals. Stacking can be used in different ways to create special rhythmical delays or to produce ambient sounds.
Ambient delay sounds
To create marvelous ambient soundscapes, you can choose two or three delay pedals.
Ideally, one or more delays should offer a modulation function.
By stacking two delays, you can create rhythmical delays.
And by choosing dissimilar delay times, the sounds will be spherical.
Therefore, you chose a short delay time and several repeats with modulation for the first delay of the signal chain and adjust an extended delay time on the following delay.
For a soundscape, both delay times ought to vary a bit more. If the times are too similar, you will create a frantic sound and phase shifting.
The second delay will also soften the attack of the repeats and makes the tone somehow blurred.
If the delay time of the second (or third) delay is not a multiple of the first delay time, the repeats of the posterior delay will be between the delays of the first pedal.
For this, I would choose darker delays like those of analog delay pedals. By this the string attack will be covered even more and the soundscapes will be marvelous.
If the delay times interact with one another, you can create alike results.
By combining a dotted eighth delay with a quarter note delay, you will get a nice pattern like you can find it in the songs of U2.
Of course, you can try out different emphases (quarter-, eighth- or sixteenth-notes.
For this experiment, I would recommend a brighter digital delay to underline the individual emphases.
Some digital delays offer the possibility to use internally two delays serial or parallel.
The Strymon DIG for example prevails this feature.
But of course, you can stack two arbitrary delays to get a likewise effect.