reverse proxy - Apache set new header not working -

i'm trying put new header called myheader request proxied backend in apache reverse proxy 2.4 using following configuration. header not getting inserted. can apache expert please

    <location /dashboard>       authtype form       sethandler form-logn-handle       authname dashboard       authformprovider dbd       authformloginrequiredlocation http://example.com/login.html       authformlogoutlocation http://example.com/logout.html       authdbduserpwquery "select cust_password table user=%s"       require valid-user       rewriteengine on       session on       sessionmaxage 6000       sessioncookiename session path=/       sessionheader x-replace-session        rewritecond %{request_filename} -f       rewritecond %{request_filename} -d       rewritecond %{la-u:remote_user} ^[a-z].*        rewriterule ^/(.*)\.(gif|jpg|png|jpeg|css|js|map|ttf|woff|woff2)$ http://localhost/dashboard/%{la-u:remote_user}/$1 [ns,nc,qsa,p,l]        rewritecond %{la-u:remote_user} ^[a-z].*       rewriterule ^/(.+)/dashboard/(.*)$ http://localhost/dashboard/%{la-u:remote_user}/$1 [ns,nc,qsa,p,l]       proxypass http://localhost/dashboard       requestheader set myheader "myheader"       header set myheader "myheader"       proxypassreverse http://localhost:80/dashboard       proxypreservehost on     </location>