I am trying to make changes to the validElements section here:

"Umbraco": {
    "CMS": {
      "RichTextEditor": {
        "ValidElements": "+a[id|style|rel|rev|hreflang|dir|lang|tabindex|accesskey|type|href|target|class],-abbr[class|style],-address[id|dir|class|style|aria-*|role|data-*],animate[*],animateMotion[*],animateTransform[*],area[shape|coords|href|alt|target|class],-article[id|dir|class|style|aria-*|role|data-*],-aside[id|dir|class|style|aria-*|role|data-*],audio[class|style|*],-b/-strong[class|style],-bdo[class],-blockquote[id|dir|style|aria-*|role|class],br[class],button[id|class|style|*],canvas[id|class|style|alt|aria-*|role|data-*|width|height|*],caption[id|lang|dir|class|style],circle[*],-cite[class|style],clipPath[*],-code[class|style],datalist[id|class|style|*],dd[id|class|title|style|dir|lang],defs[*],desc[*],-details[id|dir|class|style|aria-*|role|open],-dfn[class],discard[*],-div[id|dir|class|style|aria-*|role|data-*],dl[id|class|title|style|dir|lang],dt[id|class|title|style|dir|lang],ellipse[*],feBlend[*],feColorMatrix[*],feComponentTransfer[*],feComposite[*],feConvolveMatrix[*],feDiffuseLighting[*],feDisplacementMap[*],feDistantLight[*],feDropShadow[*],feFlood[*],feFuncA[*],feFuncB[*],feFuncG[*],feFuncR[*],feGaussianBlur[*],feImage[*],feMerge[*],feMergeNode[*],feMorphology[*],feOffset[*],fePointLight[*],feSpecularLighting[*],feSpotLight[*],feTile[*],feTurbulence[*],-fieldset[id|class|style|*],figcaption[class|style],-figure[id|dir|class|style|aria-*|role|data-*],filter[*],foreignObject[*],-form[id|class|style|*],g[*],-h1[id|dir|class|style],-h2[id|dir|class|style],-h3[id|dir|class|style],-h4[id|dir|class|style],-h5[id|dir|class|style],-h6[id|style|dir|class|style],hatch[*],hatchpath[*],hr[class|style],-i/-em[class|style],iframe[id|class|style|alt|aria-*|role|data-*|width|height|loading|src|srcdoc|allow=fullscreen|*],image[*],img[id|dir|lang|longdesc|usemap|style|class|src|alt|width|height|umbracoorgwidth|umbracoorgheight|onresize|onresizestart|onresizeend|rel|data-*],input[id|class|style|*],label[id|class|style|*],-legend[id|class|style|*],-li[id|class|style],line[*],linearGradient[*],map[id|name|class|style|aria-*|role|data-*],marker[*],mask[*],metadata[*],meter[id|class|style|*],mpath[*],-nav[id|dir|class|style|aria-*|role|data-*],-ol[id|class|reversed|start|style|type],optgroup[id|class|style|*],option[id|class|style|*],output[id|class|style|*],-p[id|style|dir|class],path[*],pattern[*],picture[id|class|style|alt|aria-*|role|data-*|width|height|loading|*],polygon[*],polyline[*],-pre[class|style],progress[id|class|style|*],-q[class|style],radialGradient[*],rect[*],-section[id|dir|class|style|aria-*|role|data-*],-select[id|class|style|*],set[*],-small[class|style],source[*],-span[class|style],stop[*],-strike[class|style],-sub[style|class],-summary[id|class|style|aria-*|role],-sup[style|class],-svg[id|class|style|alt|aria-*|role|data-*|*],switch[*],symbol[*],-table[id|class|style|dir|lang|*],tbody[id|class],td[id|lang|dir|class|colspan|rowspan|style|scope],text[*],textarea[id|class|style|*],textPath[*],tfoot[id|class],-th[id|lang|dir|class|colspan|rowspan|style|scope],thead[id|class],title[*],-tr[id|class|style|dir|lang],track[*],tspan[*],-u[class|style],-ul[id|class|style],use[*],video[id|class|style|alt|aria-*|role|data-*|*],view[*]",
"InvalidElements": "font"},

some HTML tags are being stripped out even though they have been placed in the validElements section as seen in the code above. This is quite frustrating as it is holding us back from further development. We never had this problem in previous versions using .config files.