If any issue changes its status, it changes the Resolution field. And there is no option for setting it to “Unresolved” (NULL in the Database).
On the Issue view, select the resolution field so that its dropdown becomes visible
<option value="">Unresolved</option>**
Create bookmark with following code as URL:
javascript:!function(){function%20e(e,t){t||(t=window.location.href),e=e.replace(/[\[\]]/g,%22\\$%26%22);var%20n=new%20RegExp(%22[%3F%26]%22+e+%22(=([^%26%23]*)|%26|%23|$)%22),o=n.exec(t);return%20o%3Fo[2]%3FdecodeURIComponent(o[2].replace(/\+/g,%22%20%22)):%22%22:null}function%20t(){issueId=e(%22id%22,jQuery(%22%23edit-issue%22).attr(%22href%22)),atl_token=$(%22meta[name=atlassian-token]%22).attr(%22content%22),jQuery.post(%22/secure/AjaxIssueAction.jspa%3Fdecorator=none%22,{resolution:%22%22,singleFieldEdit:!0,atl_token:atl_token,issueId:issueId},function(){document.location=document.location.href})}($=window.jQuery)%3Ft():(script=document.createElement(%22script%22),script.src=%22http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js%22,script.onload=t,document.body.appendChild(script))}();
There are two possible ways to resolve it: