Pipeline input step (https://www.jenkins.io/doc/pipeline/steps/pipeline-input-step/) multiline parameter type TextParameterDefinition is converted to single line when used at stage view popup.

Steps to reproduce:

1. For the following code:

def multiline_text = '''multiline
text'''
stage('simple-test') {
    def result = input(message: 'pipeline-input-step test', parameters: [[name: 'text_param', $class: 'TextParameterDefinition', defaultValue: multiline_text]])
    echo result
}

2. At the stage view the multiline text parameter is presented as single line:

3. Clicking button Proceed produces single line parameter result accordingly:

[Pipeline] echo
multilinetext 

Expected result:

Multiline parameter of type TextParameterDefinition sustains new line characters like it is properly supported by action Paused for Input:

(screens from Jenkins 2.346.2, Input Step Version 449.v77f0e8b_845c4)