Hi @UmerJaved ,
Do you want to add a custom "Save and Edit" button in your Web Form Step?
Do you want to add a "Edit" option in the List View?
For your first question, do you want to add a custom "Save and Edit" button in your Web Form Step? Regarding the needs that you mentioned, I afraid that there is no direct way to achieve your needs.
As an possible solution, I think custom JavaScript code could achieve your needs. Please check and see if the following blog could help in your scenario:
https://debajmecrm.com/2020/03/11/quick-tip-save-a-record-in-powerapps-portals-using-custom-button-on-entity-form/
On your side, you should open the specific Web Form Step in your Portal, then switch to "Form Options" option, then scroll down to the "Custom JavaScript" part:

$(document).ready(function() {
// Type your custom code here. Details Steps as below:
$("div.actions").append("<input type='button' id='btnSaveAndExit' name='btnSaveAndExit' value='Save and Exit' class='submit-btn btn btn-primary form-action-container-left' />")
// bind the click event to this custom buttton
$("#btnSaveAndExit").bind("click", function () {
// perform your own logic here.
WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions($(this).prev().attr("name"), '', true, '', '', false, true));
});
});
For your second question, please make sure you have enabled "Enabled Permission" option for the Case Entity List in your Portal:
then the "Edit" icon would be shown up as below:

Please try above solution, then check if the issue is solved.
Regards,