# UXP - reading/writing effect's hidden arbitrary params?

**URL:** <https://forums.creativeclouddeveloper.com/t/uxp-reading-writing-effects-hidden-arbitrary-params/12250>\
**Category:** Premiere Pro\
**Tags:** uxp\
**Created:** [October 1, 2026, 7:45pm UTC](https://forums.creativeclouddeveloper.com/t/uxp-reading-writing-effects-hidden-arbitrary-params/12250 "2026-10-01T19:45:28Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![BartW](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bartw/32/2386_2.png) [@BartW](https://forums.creativeclouddeveloper.com/u/BartW)\
**Post date:** [October 1, 2026, 7:45pm UTC](https://forums.creativeclouddeveloper.com/t/uxp-reading-writing-effects-hidden-arbitrary-params/12250/1 "2026-10-01T19:45:28Z")

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Is there a way to read/write effect’s hidden arbitrary parameters, like we could do with ExtendScript by treating them as utf-16 strings?

My probes for value reads and writes throw errors:

```auto
value reads: 
param "Plugin UUID";
timeVarying=false keyframes=false; 
getStartValue -> undefined undefined; 
getValueAtTime(0) threw getValueAtTime() is not supported for Color, MogrtText, or MogrtComment type component parameters. Use getStartValue() to get the current value of component parameters of those types.; 
getKeyframePtr(0) threw Error: Illegal Parameter type; 
raw keyframe: object 
keys=[] value: undefined keys=[]

```

```auto
writeProbe: {
"result":0,
"paramIndex":3,
"createKeyframe":"keyframe threw Error: Illegal Parameter type",
"startValue unchanged":"no keyframe",
"startValue .value = string":"keyframe threw TypeError: Cannot set properties of null (setting 'value')",
"startValue .value = {value}":"keyframe threw TypeError: Cannot set properties of null (setting 'value')",
"startValue .value.value = string":"keyframe threw TypeError: Cannot read properties of null (reading 'value')"
}

```

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<div class="post-metadata">

**Author:** ![BartW](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bartw/32/2386_2.png) [@BartW](https://forums.creativeclouddeveloper.com/u/BartW)\
**Post date:** [October 8, 2026, 10:50am UTC](https://forums.creativeclouddeveloper.com/t/uxp-reading-writing-effects-hidden-arbitrary-params/12250/2 "2026-10-08T10:50:12Z")

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Can I get any feedback on this? This capability to get/set hidden arbitrary parameter values is essential for us to be able to move on from CEP to UXP extension.

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<div class="post-metadata">

**Author:** ![ariestav](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/ariestav/32/4531_2.png) [@ariestav](https://forums.creativeclouddeveloper.com/u/ariestav)\
**Post date:** [October 8, 2026, 1:53pm UTC](https://forums.creativeclouddeveloper.com/t/uxp-reading-writing-effects-hidden-arbitrary-params/12250/3 "2026-10-08T13:53:48Z")

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@Bart While they _might_ be able to be listed, I’m doubtful that they would be able to set. As it stands a mogrt properties cannot be set by UXP, but they can be retrieved and listed.

There is a long standing thread here about this: [MOGRT Parameters in UXP availabilty - #6 by Billy\_Ward](https://forums.creativeclouddeveloper.com/t/mogrt-parameters-in-uxp-availabilty/11408/6)

While hidden params are different from mogrt params, they might fall under the same category in terms of migration from CEP to UXP.

Adobe might have more insight.