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The visible checkbox can be used (either manually or by using a display action). Variables which don't have this setting checked, won't be shown in any input form
The display filter can be used in combination with a filter in the Input Form Panel's properties. In that case, only variables with a matching filter will be shown inside the relevant panel. Multiple Panels can be configured, to show different sets of variables
Locked (New in 6.5 / 2021.1)
Locking the variable, will show a read-only version in the input panel
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For more information on display filters, see Conditional Interface Elements
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short text, long text and formatted text present the user with options for entering textual information
A calculated field has no input option at all, but has an additional document action ("Value"), which can return its value. See lower
an Image variable is presented to the user as a choice of images from a variety of repositories
A number variable is presented in the Input Form as a numeric stepper
A checkbox is visualized as a true/false checkbox
A date variable allows the user to choose a date
A list variable can be presented as a pulldown or as a list of checkboxes (with multiple items being selectable)
a table variable is presented as an input grid, and will be placed in the text frames as tab delimited text
color, paragraph style, character style and font variables allow for selection (and in some cases modification) of resource items. Note that these input types are mostly used by actions, and do not offer a lot of control over use throughout the document (see ?Common Document Actions for examples which might be more suited to your needs in those cases)
coordinate variables are presented to the user as an input of a measurement unit, taking into account the current document's viewpreferences (mm, pt, in, ...), and also allowing the basic calculations. These again are most often used by document actions
divider variables allow you to insert a divider into the Input Form
button bar variables allow you to configure buttons (or icons) with attached document actions
Structured Text (new in 6.3 & 2020.3) a variable that allows structured text in the content, mapped to styles
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