When ever you activate Flexi Plugin the few pages are created automatically for you easiness.
One of the page is ‘Post Image’ & ‘Edit Flexi Post‘ and it has various fields and this is generated with following shortcode for ‘Post Image’.

[flexi-form class="pure-form pure-form-stacked" title="Submit to Flexi" name="my_form" ajax="true"]
[flexi-form-tag type="post_title" title="Title" value="" placeholder="main title" required="true"]
[flexi-form-tag type="category" title="Select category"]
[flexi-form-tag type="tag" title="Insert tag"]
[flexi-form-tag type="article" title="Description"  placeholder="Content"]
[flexi-form-tag type="file" title="Select file" required="true"]
[flexi-form-tag type="submit" name="submit" value="Submit Now"]
[/flexi-form]

• Title
• Category
• Tag
• Description
• Select File
• Submit button

This page is generated with

Title

Select file No file selected

shortcode and each fields is inserted with shortcode.
All you have to do is remove that shortcode from the page.
For example you want to remove ‘Tag & Description’ from the page.

Tag has shortcode of

Insert tag

& Description has shortcode

Description

So, edit the page where which has the form and remove that shortocode. Which results the shortcode as below.

[flexi-form class="pure-form pure-form-stacked" title="Submit to Flexi" name="my_form" ajax="true"]
[flexi-form-tag type="post_title" title="Title" value="" placeholder="main title" required="true"]
[flexi-form-tag type="category" title="Select category"]
[flexi-form-tag type="file" title="Select file" required="true"]
[flexi-form-tag type="submit" name="submit" value="Submit Now"]
[/flexi-form]

Save or Publish the changes. Now it will have fields as

• Title
• Category
• File
• Submit

Similarly, if you have activated Flexi-PRO can let users to modify the submitted post. Which is dynamically created as ‘Edit Flexi Post‘ page. This page can also be modified as above steps.